(427h) Detoxification of Halogenated Aromatic Compounds By Anaerobic Cultures

PolyBrominated diphenyl ethers (PBDEs) and Polychlorinated biphenyls (PCBs) are widespread global contaminants due to their widespread industrial usage and improper disposal. They are classified as persistent organic pollutants (POPs) and are known for their endocrine disrupting behavior, neurotoxicity, and possible human carcinogenicity. At the contaminated sites, PBDEs and PCBs frequently coexist with other halogenated compounds such as chloroethanes, and chloroethenes. The presence of multiple halogenated compounds usually poses toxicity to dehalogenating microbes, because few dehalogenating cultures are capable of detoxifying a broad spectrum of halogenated compounds. So far, little is known about microorganisms that carry out dehalogenation of these congeners under anaerobic conditions. Here we report an anaerobic culture capable of reductively debrominating congener 47 (100% removal), congener 99 (88% removal), and congener 100 (92% removal) to the non-brominated diphenyl ether within 2-4 weeks. We also obtained a sediment-free culture which is able to sequentially remove halogens from PCBs and other halogenated compounds. For example, this culture dechlorinates the commercial PCB mixture - Aroclor 1260 - mainly by removing flanked para- and doubly flanked meta- chlorines, debrominates octa-brominated diphenyl ether (octa-BDE) mixture predominantly to tetra-BDEs, and dechlorinates tetrachloroethene (PCE)/1,2-dichloroethane (1,2-DCA) completely to ethene. The 16S rRNA gene-based techniques revealed that Dehalococcoides are the dechlorinators in both cultures. Quantitative PCR results showed that the growth of Dehalococcoides linked tightly with PBDE/PCBs debromination. Given the ubiquity and recalcitrance of PBDEs/PCBs, the anaerobic cultures are promising for bioremediation applications in the restoration of halogenated compounds contaminated environments.